An internal combustion engine (ICE) for a motor vehicle generally includes an engine block which defines at least one cylinder accommodating a reciprocating piston coupled to rotate a crankshaft. The cylinder is closed by a cylinder head that cooperates with the reciprocating piston to define a combustion chamber. A fuel and air mixture is cyclically disposed in the combustion chamber and ignited, thereby generating hot expanding exhaust gasses that cause the reciprocating movements of the piston. The fuel is injected into each cylinder by a respective fuel injector. The fuel is provided at high pressure to each fuel injector from a fuel rail in fluid communication with a high pressure fuel pump that increase the pressure of the fuel received from a fuel source.
Generally speaking, internal combustion engines are currently operated with multi-injection patterns, namely for each engine cycle, a train of several injection pulses is performed. A typical train of injections may start from a pilot injection pulse being followed by one or more pre-injections, by main injection pulse, eventually terminating with one or more after and/or post injections.
For each of these injections an Electronic Control Unit (ECU) may receive input signals representative of various physical parameters associated with the ICE from various sensors and may execute suitable calculation tasks to determine the relevant physical parameters of each fuel injection as a function of several factors, such as the above received signals, engine speed, engine torque request, rail pressure, after-treatment procedures and the like. The fuel injectors are then actuated according to the calculated parameters.
As it is known in the art, the most important injection parameters are the Start of Injection (SOI) which indicates the time value at which an injection is started and the Energizing Time (ET) of the fuel injector which indicates the length of time during which a fuel injector is energized during an injection pulse. Furthermore, the Dwell Time (DT) indicates the time interval included between two consecutive injection pulses, namely the time interval between the end of the Energizing Time (ET) of a first injection pulse and the Start of Injection (SOI) of a second consecutive injection pulse. Timing of the SOI may be measured in degrees of the crank angle of the piston before top dead center (BTDC), which is the highest position the piston reaches in the cylinder.
In order to calculate the parameters of a train of injection pulses, it is known in the art of engine control to perform in succession two ECU tasks, namely LORES Compression task and DI_Scheduling task. The LORES Compression task estimates: pulses number, pulses fuel quantities, start of injection (SOI) and DT (Dwell Time) for all pulses. Moreover, the LORES Compression task also calculates the angular position of the start of the calculations of the following DI_Scheduling task. The DI_Scheduling task calculates all Energizing Times (ET) for all pulses on the basis of the previous data and on a rail pressure sampled value.
However, there is a certain time delay between the start of the DI_Scheduling task start and the first instant of the injection actuation. This delay is due to the time needed by the electronic controller unit to run all computations that must be performed in the DI_Scheduling task. During this delay, engine conditions such as engine speed or rail pressure may change and this phenomena may cause injection inaccuracy and injection s effects not in line with the real expectations of the driver and with the engine conditions in that moment.